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Thread: Galactic Rotation and Dark Matter

  1. #1

    Galactic Rotation and Dark Matter


    The Dark Matter Myth
    Magnetic Fields and Galactic Rotation Curves


    Introduction
    The shape of galactic rotation curves (i.e. the galactic rotation velocity as a function of the distance from the galactic center), has led astronomers to the conclusion that galaxies must be surrounded by an invisible massive halo of 'dark matter' which exceeds the visible mass by up to 10 times (see http://ned.ipac.caltech.edu/level5/March01/Battaner/ for a detailed review of the Dark Matter theory and 'observations' ; for a more popular account see http://www.owlnet.rice.edu/~spac250/elio/spac.html).
    The underlying assumption with this model is that gravity is the only force determining the dynamics of the galaxy. However, practically all rotation curves indicating the existence of dark matter have been obtained by observing the Doppler shift of gas (usually the 21 cm line of hydrogen) rather than of stars. It is generally assumed that the gas provides a tracer for the motion of the stars, but this assumption neglects the fact that ionized atoms are very much affected by electromagnetic forces: it is easy to show that with the generally assumed galactic magnetic field of 10^-6 Gauss, the Lorentz force on a thermal proton is about 10 orders of magnitude stronger than the gravitational force (assuming a galaxy of the mass and size of the Milky Way) and should therefore completely determine the dynamics of the plasma, which in turn should also have an impact on the neutral gas because of recombination. Even a large additional amount of dark matter would therefore not exclusively determine the galactic gas dynamics.
    Note: It is surprising that the dark matter theory has not been challenged yet on grounds of general scientific implausibility alone: as the mass of the dark matter is usually many times the normal mass of the galaxy, it would be bizarre to assume that the formation of the dark matter halo has been triggered by the normal matter (one might as well assume that the planets are responsible for the formation of the sun). One would have to conclude therefore that, on the contrary, the dark matter has led to the formation of the visible galaxy. This however would mean that all galaxies should show evidence for dark matter, which is clearly not the case.

    Magnetic Field Lines and Lorentz Force
    A magnetic field line is an imaginary line along which the Lorentz force FL= q/c*vxB = 0. This condition effectively defines the direction of the magnetic field B. However, the Lorentz force is not only zero if v is parallel to B, but also if v is zero. As velocities are by definition relative, a preferred reference frame defining v and therefore FL uniquely has to be specified. It is obvious that this can only be given by the physical object producing the magnetic field (a circumstance commonly neglected in electrodynamics). For a magnetic field produced dynamically by a plasma current (dynamo), the velocity v in the Lorentz force has therefore to be referred to the average velocity of the plasma ions in the dynamo region (as these constitute the main mass of the current system).

    Plasma- and Gas Dynamics in the Galactic Magnetic Field
    The galactic magnetic field can be assumed to be produced by a rotating plasma (dynamo region) in the more central region of the galaxy, i.e. the velocity v in the Lorentz force term has to be referred to the rotational velocity vD of this region (vD itself refers obviously to the center of the galaxy).
    As vD is not constant throughout the dynamo region, one would in principle have to perform an average over the whole volume, but since the magnetic field strength produced by each sub-region decreases with distance, one can assume as a first order approximation that vD is determined by the dynamo region closest to the point in question.
    Only charged particles with a velocity v=vD will therefore not experience any Lorentz force, i.e. this is the speed with which the plasma will be dragged along by the magnetic field. Because the condition v=vD is independent of the distance from the dynamo region, the rotation curve of the plasma is consequently constant in the outer regions of the galaxy, as observed (see illustration below). The neutral gas is of course not immediately affected by the magnetic field, but once an atom becomes ionized, it will be imparted the velocity vD by the magnetic field. If the ion recombines it will maintain the tangential speed despite not being trapped anymore by the magnetic field. If this speed exceeds the gravitational escape velocity, the atom will then escape from the galaxy. The ionization rate of the neutral gas varies obviously quite strongly throughout the galaxy, but one can estimate that a neutral atom in interstellar space is ionized after 10^6-10^9 years which is smaller or at least about equal to the dynamical time scale of the galaxy, so that most of the neutral gas should appear to co-rotate with the plasma. Because of the conservation laws of mechanics, the dynamo region must therefore continuously lose energy as well as angular momentum. This circumstance could well explain the slightly increasing rotation curve for some galaxies if one assumes a more extended dynamo region (in a different context, this mechanism could also account for the apparent loss of angular momentum in the process of star formation). On the other hand, rotation curves decreasing with distance could indicate that the (rotating) galactic magnetic field blends into the (near-stationary) intergalactic magnetic field.
    The plasma dynamics in the magnetic field of galaxies could in this sense explain most of the rotation curves seen as an evidence for dark matter.



    Schematic representation of galactic gas rotation:
    the plasma at the rim of the central dynamo region rotates with velocity vD. Therefore the magnetic field lines outside the dynamo region rotate with the same velocity (v=vD), dragging the plasma with them.


    Note: the above is a copy of my webpage http://www.physicsmyths.org.uk/darkmatter.htm.

  2. #2
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    Re: Galactic Rotation and Dark Matter

    Quote Originally Posted by Thomas
    However, practically all rotation curves indicating the existence of dark matter have been obtained by observing the Doppler shift of gas (usually the 21 cm line of hydrogen) rather than of stars. It is generally assumed that the gas provides a tracer for the motion of the stars, but this assumption neglects the fact that ionized atoms are very much affected by electromagnetic forces:
    Well, this is a horribly problematic statement for one because the 21 cm line is a tracer not of ionized hydrogen but of neutral hydrogen.

    and should therefore completely determine the dynamics of the plasma, which in turn should also have an impact on the neutral gas because of recombination.
    And the details of this are what? Any ionized gas in the disk is going to necessarily be of far lower density than the neutral gas. There is a connection via recombination, but that doesn't explain how the gas dynamics are effected by ionization when most of the gas never goes through such a phase.

    Even a large additional amount of dark matter would therefore not exclusively determine the galactic gas dynamics.
    Of course, we have more evidence for dark matter than simply from rotation curves:

    1) Cluster gas dynamics that is on scales so huge your magnetic fields cannot explain them since they'd have to be too enormous.

    2) Gravitational Lensing. This is totally unaffected by any dynamical models at all.

    3) Cluster dispersion velocities. Galaxies in clusters are assumed to be virialized near the center, but are moving around too fast to explain the matter that is visible. Thus, more dark matter.
    [i]Note: It is surprising that the dark matter theory has not been challenged yet on grounds of general scientific implausibility alone: as the mass of the dark matter is usually many times the normal mass of the galaxy, it would be bizarre to assume that the formation of the dark matter halo has been triggered by the normal matter (one might as well assume that the planets are responsible for the formation of the sun).
    The origins of a nonbaryonic component of the dark matter and the fact that it is cold is a theory derived from cosmology and not from observation. Nevertheless, the baryon density is robustly determined by the thermodynamics and kinematics of the Big Bang that we have probed not just with Hubble Models but also with the CMB. Most importantly, the cosmic deteurium abundance places a tremendous constraing on Omega-baryon, thus establishing that the structure building component is not normal matter but something collisionless, cold, and yet unseen.

    One would have to conclude therefore that, on the contrary, the dark matter has led to the formation of the visible galaxy. This however would mean that all galaxies should show evidence for dark matter, which is clearly not the case.
    Give us an example of a galaxy that doesn't show evidence for dark matter.

    The neutral gas is of course not immediately affected by the magnetic field, but once an atom becomes ionized, it will be imparted the velocity vD by the magnetic field. If the ion recombines it will maintain the tangential speed despite not being trapped anymore by the magnetic field.
    As I said, the majority of neutral gas never experiences ionization.

    The ionization rate of the neutral gas varies obviously quite strongly throughout the galaxy, but one can estimate that a neutral atom in interstellar space is ionized after 10^6-10^9 years which is smaller or at least about equal to the dynamical time scale of the galaxy,
    Don't think so. This time scale doesn't jive as far as I'm concerned. The only place you get ionization is in Stromgren Spheres, and their filling factor is so small that your average atom never sees them.

    On the other hand, rotation curves decreasing with distance could indicate that the (rotating) galactic magnetic field blends into the (near-stationary) intergalactic magnetic field.
    Which poses a problem for your model since clusters also show a large amount of dark matter. Since cluster dark matter cannot be explained by magnetic fields, I'm afraid your theory has to bifurcate at this point.

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    Re: Galactic Rotation and Dark Matter

    Quote Originally Posted by JS Princeton
    Give us an example of a galaxy that doesn't show evidence for dark matter.
    Any elliptical galaxy, evidently
    Everything I need to know I learned through Googling.

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    cyreks comment:
    I agree with Thomas here with his opening statement that the dark matter around our galaxy which is ten times greater is unbelievable. As a matter of fact, it is absolutely ludicrous.

    My post on 'dark matter' here in the BABB is the simplist and the most realistic explanation.
    The small number of negative hydrogen ions in the outer gaseous perimeter of our galaxy interacting with the inner positive ions of our galaxy, create the apparent mass that does not exist. It would take a very small amount of these seperated charges to enhance the gravitational effect of the spiral structure by a factor of ten because of the enormously greater strength of the electric force as compared to gravity.

  5. #5

    Re: Galactic Rotation and Dark Matter

    Quote Originally Posted by JS Princeton
    Well, this is a horribly problematic statement for one because the 21 cm line is a tracer not of ionized hydrogen but of neutral hydrogen.
    This is correct, but each neutral atom is ionized at certain stages of its existence. It is during this stage that the magnetic field will speed it up to a velocity consistent with its rotation. After recombination it will maintain this velocity.

    Quote Originally Posted by JS Princeton
    Any ionized gas in the disk is going to necessarily be of far lower density than the neutral gas. There is a connection via recombination, but that doesn't explain how the gas dynamics are effected by ionization when most of the gas never goes through such a phase.
    see above


    Quote Originally Posted by JS Princeton
    Of course, we have more evidence for dark matter than simply from rotation curves:
    I have not done any closer investigation into the other 'evidences' for dark matter yet, but I am sure there are answers to this within conventional physics as well.
    Fact is that galactic rotation curves constitute the main 'evidence' for it (historically anyway) and that the underlying theory on which this conclusion is reached is simply incomplete in terms of conventional physics (as outlined in my opening post).

    Quote Originally Posted by JS Princeton
    Give us an example of a galaxy that doesn't show evidence for dark matter.
    Check out the first link in my opening post somewhat closer, and you can find numerous mentions of galaxies that do not show conclusive signs of dark matter (even with the conventional interpretation of rotation curves that is).

    The ionization rate of the neutral gas varies obviously quite strongly throughout the galaxy, but one can estimate that a neutral atom in interstellar space is ionized after 10^6-10^9 years which is smaller or at least about equal to the dynamical time scale of the galaxy,
    Quote Originally Posted by JS Princeton
    Don't think so. This time scale doesn't jive as far as I'm concerned. The only place you get ionization is in Stromgren Spheres, and their filling factor is so small that your average atom never sees them.
    I made an estimate based on the sun's UV radiation flux and the average distance of stars in the galaxy which yielded about 10^9 years for the time after which a neutral atom becomes ionized (this neglects even cosmic rays or other potential ionization sources). It is clear that in the closer vicinity of stars this time will be substantially shorter.
    As long as this time is not much longer than the time scale on which the neutral gas is 'recycled' through large scale transport processes, the ionization should therefore affect the neutral gas dynamics significantly.

    On the other hand, rotation curves decreasing with distance could indicate that the (rotating) galactic magnetic field blends into the (near-stationary) intergalactic magnetic field.
    Quote Originally Posted by JS Princeton
    Which poses a problem for your model since clusters also show a large amount of dark matter. Since cluster dark matter cannot be explained by magnetic fields, I'm afraid your theory has to bifurcate at this point.
    This is not how science works. If you submit an article to a peer reviewed journal and the referee detects an error or omission in the theory on which your data analysis is based, then you have to redo the data analysis with the modified theory, but you can't say: 'but there is other evidence that my conclusions are correct'.
    What I am saying here is that the papers purporting to prove the existence of 'dark matter' through the analysis of galactic rotation curves should not have been accepted in the first place because of the point explained in my opening post.
    this is not to say that I support the peer review system in its present form. It is too often abused by referees to consolidate their own scientific position and block any critical work. Also, it has become prohibitively expensive, in particular for individuals, to get their work published in print. The internet will soon make the present system redundant anyway, as everybody can publish their own work with a minimal cost and everybody can make up their own mind about the scientific value of an article without being patronized by a self-appointed board of censors

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    Michael Cyrek: "I agree with Thomas here with his opening statement that the dark matter around our galaxy which is ten times greater is unbelievable. As a matter of fact, it is absolutely ludicrous."

    Ho! But critics of quantum theory said much the same thing, as did critics of relativity theory. The universe is not constrained to behave in ways you or I, personally, find believable.

    ------

    Nicely detailed post, Thomas. Good to see.

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    Quote Originally Posted by Thomas
    Only charged particles with a velocity v=vD will therefore not experience any Lorentz force, i.e. this is the speed with which the plasma will be dragged along by the magnetic field.
    Backward physics. Its the plasma that does the dragging, not the field. Besides, the only way to exert a force on a charge with a magnetic field is through Faraday induction, which depends on dB/dt, and I don't see that in your first post anywhere. So even if the neutral gas becomes ionized, there's no way the magnetic field can add energy to the plasma unless there's a dB/dt between the plasma & the field.

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    cyrek1 wrote: The small number of negative hydrogen ions in the outer gaseous perimeter of our galaxy interacting with the inner positive ions of our galaxy, create the apparent mass that does not exist.
    Did I miss something in the literature? Is there evidence that there is a reservoir of NEGATIVE hydrogens ions in the outer galaxy. If it is true is there evidence that they are not found in the inner regions of the galaxy? If the answer is "yes" to both of these questions, then what is the mechanism that generates this supply of negative H ions?

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    Quote Originally Posted by Thomas
    It is generally assumed that the gas provides a tracer
    You rang?

  10. #10
    Quote Originally Posted by Tim Thompson
    Quote Originally Posted by Thomas
    Only charged particles with a velocity v=vD will therefore not experience any Lorentz force, i.e. this is the speed with which the plasma will be dragged along by the magnetic field.
    Backward physics. Its the plasma that does the dragging, not the field. Besides, the only way to exert a force on a charge with a magnetic field is through Faraday induction, which depends on dB/dt, and I don't see that in your first post anywhere. So even if the neutral gas becomes ionized, there's no way the magnetic field can add energy to the plasma unless there's a dB/dt between the plasma & the field.
    Backward physics? Only if you view the problem from the wrong end.
    Assume you have a magnet with an electron moving in a circle around one of its field lines. Are you saying then that the electron would not move with the magnet if you move the latter ?

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    Re: Galactic Rotation and Dark Matter

    Quote Originally Posted by ToSeek
    Quote Originally Posted by JS Princeton
    Give us an example of a galaxy that doesn't show evidence for dark matter.
    Any elliptical galaxy, evidently
    The ellipticals still have dark matter, it just looks like their halos aren't as extended (or more exactly, these galaxies fill their halos with luminous matter more completely).

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    Quote Originally Posted by cyrek1
    My post on 'dark matter' here in the BABB is the simplist and the most realistic explanation.
    The small number of negative hydrogen ions in the outer gaseous perimeter of our galaxy interacting with the inner positive ions of our galaxy, create the apparent mass that does not exist. It would take a very small amount of these seperated charges to enhance the gravitational effect of the spiral structure by a factor of ten because of the enormously greater strength of the electric force as compared to gravity.
    Trivially disproven. Ionized particles are visible, michael... dark matter isn't.

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    Re: Galactic Rotation and Dark Matter

    Quote Originally Posted by Thomas
    each neutral atom is ionized at certain stages of its existence. It is during this stage that the magnetic field will speed it up to a velocity consistent with its rotation. After recombination it will maintain this velocity.
    You don't have ionization taken place long enough. The FACT remains that the neutral gas is ionized for too short a time to be accelerated to the speeds needed to explain your effect.

    More than that, in order to really explain it since the magnetic fields decrease as you increase radius, neutral gas on the outskirts of the galaxy will have to be ionized LONGER than neutral gas interior (so that you can get up to the proper orbital velocity speeds). The opposite is actually the case.

    I have not done any closer investigation into the other 'evidences' for dark matter yet, but I am sure there are answers to this within conventional physics as well.
    Fact is that galactic rotation curves constitute the main 'evidence' for it (historically anyway) and that the underlying theory on which this conclusion is reached is simply incomplete in terms of conventional physics (as outlined in my opening post).
    This is conjecture from ignorance. Your "certainty" is an excellent indication that you aren't engaging in scientific discourse but rather self-promoting grandstanding.

    Quote Originally Posted by JS Princeton
    Check out the first link in my opening post somewhat closer, and you can find numerous mentions of galaxies that do not show conclusive signs of dark matter (even with the conventional interpretation of rotation curves that is).
    Non-answer. The fact remains that EVERY GALAXY ever observed has evidence and we don't see a correlation, for example, between galaxies with high magnetic fields and the amount of dark matter. If your effect was true, that's what we should see. Again, another problem with your analysis.

    I made an estimate based on the sun's UV radiation flux and the average distance of stars in the galaxy which yielded about 10^9 years for the time after which a neutral atom becomes ionized (this neglects even cosmic rays or other potential ionization sources).
    Horribly bad approximation because you realize that there are characteristic SIZES to how far UV-radiation can go. In particular, once a UV photon is absorbed, it is destroyed. UV photons from the sun don't ever reach the next star. Your view of ionization is wrong and is shown to be by any introductory text on the interstellar medium.

    It is clear that in the closer vicinity of stars this time will be substantially shorter.
    Backwards. The closer you are to a star, the more things are ionized (and the longer they are ionized).

    As long as this time is not much longer than the time scale on which the neutral gas is 'recycled' through large scale transport processes, the ionization should therefore affect the neutral gas dynamics significantly.
    See above. Your analysis is wrong and shown to be so trivially because you don't take into account the fact that UV photons are destroyed upon ionizing an atom.

    By the way, the reason they're destroyed is because of the "cascade" effect. When recombination occurs, a likely cascade photon shower is likely to occur which will result in lower energy photons rather than a single high energy UV photon. This means that ionization cannot occur beyond the Stromgren Radius for a given star. It's ridiculously close to the star for everything but the hottest O and B type stars.

    What I am saying here is that the papers purporting to prove the existence of 'dark matter' through the analysis of galactic rotation curves should not have been accepted in the first place because of the point explained in my opening post.
    All of these considerations were made back when Rubin presented her work. People bent over backwards trying to explain away Dark Matter. Solutions such as yours were not proposed because they were trivially disproven, but other solutions were proposed and some still have some thrashing life left.

    By the way, Thomas, you didn't address any of my critiques. This implies to me that you didn't do your research before coming up with this idea. Best to learn about the subject in great detail before you begin to "prove" it's wrong.

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    Re: Galactic Rotation and Dark Matter

    Quote Originally Posted by ToSeek
    Quote Originally Posted by JS Princeton
    Give us an example of a galaxy that doesn't show evidence for dark matter.
    Any elliptical galaxy, evidently
    Here is another example - and this one is a nearby isolated SO galaxy (NGC 404) so that the hypothesis that the dark matter might be stripped from the E/SO galaxies doesn't work in this case. But if that was the explanation shouldn't we see it in the spirals in clusters too?

    http://adsabs.harvard.edu/cgi-bin/np...e5c03c80a07384

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    Thomas wrote: This is not how science works. If you submit an article to a peer reviewed journal and the referee detects an error or omission in the theory on which your data analysis is based, then you have to redo the data analysis with the modified theory, but you can't say: 'but there is other evidence that my conclusions are correct'.
    Not necessarily modify the theory. I've received referee reports in which the referee finds the analysis sound but wants to see more support for the conclusions.

    What I am saying here is that the papers purporting to prove the existence of 'dark matter' through the analysis of galactic rotation curves should not have been accepted in the first place because of the point explained in my opening post.
    You might want to check out the "Expanding Universe - another direction" thread because Plasma Cosmology has been debated there for a while. But as much as I'm not convinced that non-baryonic dark matter will still be the explanation in 100 years (JS you may want to sit down before you read the rest of this sentence ) I would have to say that at this time it is the most scientifically valid explanation for the rotation curves of spiral galaxies.

    this is not to say that I support the peer review system in its present form. It is too often abused by referees to consolidate their own scientific position and block any critical work.
    It is really hit or miss on referee's - and the scientific editors that oversee the refereeing of the paper - if you're trying to publish controversial views. From my experience, some referee's are tolerant of alternate views as long as the analysis is sound. Other referee's demand that the evidence for a controversial view be extremely compelling - even if they acknowledge the basic analysis looks sound.

    Also, it has become prohibitively expensive, in particular for individuals, to get their work published in print. The internet will soon make the present system redundant anyway, as everybody can publish their own work with a minimal cost and everybody can make up their own mind about the scientific value of an article without being patronized by a self-appointed board of censors
    There are journals out there that will publish your research without page charges. Monthly Notices of the Royal Astronomical Society and Astrophysics & Space Science are two examples. But the most widely read journals (ApJ and ApJ letters, A&A, AJ) do have page charges.

    What you have to realize is that you must at least try to go through the peer review process if you want to convince the scientific community to look at your results. A significant part of that is referencing other people's research published in the Journals. Did I miss the references on your site? If you have not added them you should because it would go a long way toward demonstrating that you are taking a scientific approach.

    Good luck!

  16. #16

    Re: Galactic Rotation and Dark Matter

    Quote Originally Posted by JS Princeton
    By the way, Thomas, you didn't address any of my critiques. This implies to me that you didn't do your research before coming up with this idea. Best to learn about the subject in great detail before you begin to "prove" it's wrong.
    I addressed all of your critiques. The point is that apparently you still do not quite understand the mechanism I suggested:

    If an atom is ionized, it is immediately trapped by the magnetic field and moves in a Larmor circle around the local magnetic field line (this happens on a timescale given by the gyro- frequency and is about 100 sec for an ion in a magnetic field of 10^-6 Gauss). If the field line is moving itself, the ion will therefore be dragged along with the field line. This does not depend on the magnetic field strength but only on the effective velocity with which the 'magnet' is rotating.

    The relevant time here is the time the atom stays neutral, not the time the ion stays ionized (as already mentioned, the neutral atom maintains the velocity of the ion at the moment of recombination; if there is an overall rotation of the magnetic field, the corresponding neutral atoms will therefore have a corresponding velocity component). This time obviously becomes shorter for higher ionizing radiation intensities i.e. in the vicinity of stars.
    If this time is of the order of a galactic rotation, then one can say that after about one galactic rotation all neutral atoms will (on average) have been briefly ionized once and thus aquired the rotational speed of the magnetic field.
    The calculation of the time an atom stays neutral in interstellar space can be estimated from the solar UV flux shortward of 911 A, which is about 10^12 ph/cm^2/sec at the earth (1AU distance from the sun). At 1 pc (= 2*10^5 AU) this intensity is reduced to 25 ph/cm^2/sec (assuming no absorption, see below). Multiplying this with a photo-ionization cross section of 10^-17 cm^2 yields an ionization frequency of 2.5*10^-16/sec which corresponds to about 10^8 years.

    Regards the UV absorption:
    if you assume a hydrogen density of 0.1 cm^-3 (see http://casa.colorado.edu/Publication...ayaug/283.html ), then, with a photo-ionization cross section of 10^-17 cm^2, you get a mean free path of the UV radiation of 10^18 cm, i.e. about 1 lightyear. Also, a significant fraction of the photoelectrons (about 50% for electrons with an energy of 1 Rydberg (13.6 eV); see my website http://www.plasmafacts.de/recrsect.htm) will recombine into the ground state again, therewith restoring the UV photon. The UV radiation can therefore well penetrate into the interstellar medium.
    There is the further theoretical possibility of auto-ionization in the course of collisions of neutral atoms, which I have suggested to explain the nightime density of the earth's ionosphere (see my website http://www.plasmaphysics.org.uk/#auto). This would be completely independent of any radiation flux.
    Also, as already mentioned, other sources like cosmic rays supernova explosions etc. could produce ionization.

    This shows that my proposed mechanism can well fulfill the required conditions considering the uncertainties in some of the above figures (it is not necessary anyway that all galaxies fulfill the condition; after all, not all galaxies (including our own) show conclusive evidence of 'dark matter').

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    Re: Galactic Rotation and Dark Matter

    Quote Originally Posted by dgruss23
    Here is another example - and this one is a nearby isolated SO galaxy (NGC 404) so that the hypothesis that the dark matter might be stripped from the E/SO galaxies doesn't work in this case. But if that was the explanation shouldn't we see it in the spirals in clusters too?

    http://adsabs.harvard.edu/cgi-bin/np...e5c03c80a07384
    I don't know that I buy the stripping hypotheses, but one thing I can say we are overlooking is the fact that dark matter is present in these galaxies by simple Keplerian arguments. It may not be there in the same amount as in other galaxies, but it is still there.

    By the way, the rationale for why spirals in clusters shouldn't exhibit the change is because the idea goes that spirals haven't had time to interact with the dynamics of the cluster yet (only the older E/SOs). As I said, I'm not necessarily in agreement that this is the explanation, but it certainly isn't outside the realm of possibility.

    Just to reiterate, every galaxy we've so far named has shown evidence of annamolous dynamics indicating SOMETHING isn't right about the way the matter is interacting. They all have dark matter indications, even if they don't extend all the way out to large halo distances.

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    Quote Originally Posted by dgruss23
    But as much as I'm not convinced that non-baryonic dark matter will still be the explanation in 100 years (JS you may want to sit down before you read the rest of this sentence ) I would have to say that at this time it is the most scientifically valid explanation for the rotation curves of spiral galaxies.
    I always knew you were a reasonable person, dgruss!

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    Re: Galactic Rotation and Dark Matter

    Quote Originally Posted by Thomas
    If an atom is ionized, it is immediately trapped by the magnetic field and moves in a Larmor circle around the local magnetic field line (this happens on a timescale given by the gyro- frequency and is about 100 sec for an ion in a magnetic field of 10^-6 Gauss). If the field line is moving itself, the ion will therefore be dragged along with the field line. This does not depend on the magnetic field strength but only on the effective velocity with which the 'magnet' is rotating.
    This is an entirely different comment from your statement about how long atoms stay ionized which I showed to be not a correct estimation. The problem with this argument is that for short magnetization periods at large distances you don't build up the dynamical solutions you need. For example:
    The relevant time here is the time the atom stays neutral, not the time the ion stays ionized (as already mentioned, the neutral atom maintains the velocity of the ion at the moment of recombination.
    The obvious problem with this argument is that after the magnetic moment is turned off there is no longer anything accelerating your atoms. They will not rotate in spiral galaxies and they will by thermodynamically unstable to the faster speeds if there is no consistent acceleartion. Gravity provides a mechanism that doesn't degrade. A magnetic force that turns off and on does not provide this mechanism. In short, you need to have ionization occur much more often than you do, and in particular you need it to occur much more often the farther out you go from the nucleus. These are both very difficult constraints and I think they basically spell disaster for your idea.

    If this time is of the order of a galactic rotation, then one can say that after about one galactic rotation all neutral atoms will (on average) have been briefly ionized once and thus aquired the rotational speed of the magnetic field.
    And then slowed down through cooling processes. Not to mention the fact that they will not go in the preferential roational fashion as they aren't being accelearted. Completely problematic.

    The calculation of the time an atom stays neutral in interstellar space can be estimated from the solar UV flux shortward of 911 A, which is about 10^12 ph/cm^2/sec at the earth (1AU distance from the sun). At 1 pc (= 2*10^5 AU) this intensity is reduced to 25 ph/cm^2/sec (assuming no absorption, see below). Multiplying this with a density of 0.1 cm^-3 (see reference below) and assuming an ionization cross section of 10^-17 cm^2 yields an ionization frequency of 2.5*10^-17/sec which corresponds to about 10^9 years.
    You CANNOT assume no absorption out to 1 pc. I cannot access your URL as written, but if it says that no absorption out to 1 pc is reasonable, there is something wrong.
    Regards the UV absorption:
    then, with a photo-ionization cross section of 10^-17 cm^2, you get a mean free path of the UV radiation of 10^18 cm, i.e. about 1 lightyear.
    This is a characteristic size of a Stromgren Sphere. It is not due to a solar-type star. Also, the mean free path is effective due to the fact that the Stromgren Sphere (the HII region) is ionized already and thus transparent to the photons. The equilibrium occurs at 1 pc for a normal O or B type star. This is not an adequate analysis for all stars in the galaxy by any means.

    Also, a significant fraction of the photoelectrons (about 50% for electrons with an energy of 1 Rydberg (13.6 eV); see my website http://www.plasmafacts.de/recrsect.htm) will recombine into the ground state again, therewith restoring the UV photon.
    This is absolutely wrong. The electrons recombine to higher energy levels before reaching ground state. It is thermodynamically favorable for them NOT to recombine to the ground state because the energy difference represents a good estimation of cross-section. Rather, electron capture almost uniformly occurs to higher states. Even if you get a recombination quickly to the ground state, you will still tend to destroy the UV photon before it leaves the ionization sphere by simply having it reionize a nearby atom rather than escape. The UV radiation can therefore well penetrate into the interstellar medium.

    There is the further theoretical possibility of auto-ionization in the course of collisions of neutral atoms, which I have suggested to explain the nightime density of the earth's ionosphere (see my website http://www.plasmaphysics.org.uk/#auto). This would be completely independent of any radiation flux.
    Collisional ionization is nearly impossible. The temperatures required are absolutely enormous.

    This shows that my proposed mechanism can well fulfill the required conditions considering the uncertainties in some of the above figures (it is not necessary anyway that all galaxies fulfill the condition; after all, not all galaxies (including our own) show conclusive evidence of 'dark matter').
    Again, show me a galaxy that has no conclusive evidence for the extra velocity.

  20. #20
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    dgruss23 wrote:

    Here is another example - and this one is a nearby isolated SO galaxy (NGC 404) so that the hypothesis that the dark matter might be stripped from the E/SO galaxies doesn't work in this case. But if that was the explanation shouldn't we see it in the spirals in clusters too?

    http://adsabs.harvard.edu/cgi-bin/np...e5c03c80a07384


    JS princeton wrote: I don't know that I buy the stripping hypotheses, but one thing I can say we are overlooking is the fact that dark matter is present in these galaxies by simple Keplerian arguments. It may not be there in the same amount as in other galaxies, but it is still there.
    But this galaxy was shown in the paper above to have a Keplerian decline in rotation curve and they concluded that no dark matter is required to explain the behavior of this galaxy - and the HI observations do extend beyond the optical disk. I find it interesting although I'm not sure what - if anything - it means. At the minimum - assuming the observation and conclusion is correct - it would make it incorrect to say that no galaxies have been discovered which do not have significant amounts of dark matter.


    JS wrote: By the way, the rationale for why spirals in clusters shouldn't exhibit the change is because the idea goes that spirals haven't had time to interact with the dynamics of the cluster yet (only the older E/SOs). As I said, I'm not necessarily in agreement that this is the explanation, but it certainly isn't outside the realm of possibility.
    I don't know about this one. We talked about the strange peculiar motion pattern in the Virgo cluster. Assuming that those are real motions, then some of those galaxies should have passed through the cluster core enough times to have some effect. Actually, I've got a recent paper by Vera Rubin in my files that notes peculiarities in Virgo spiral rotation curves. I'll take another look at that paper.

  21. #21
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    Quote Originally Posted by dgruss23
    But this galaxy was shown in the paper above to have a Keplerian decline in rotation curve and they concluded that no dark matter is required to explain the behavior of this galaxy - and the HI observations do extend beyond the optical disk.
    Beyond the optical disk, I realize that we may even approximate a M/L ratio of 1, but I'm not convinced that the data show a M/L across the galaxy of 1. Where did you read that? All I see as that, although there is a higher M/L ratio, it dies off appropriately.

    I find it interesting although I'm not sure what - if anything - it means. At the minimum - assuming the observation and conclusion is correct - it would make it incorrect to say that no galaxies have been discovered which do not have significant amounts of dark matter.
    See above.

    I don't know about this one. We talked about the strange peculiar motion pattern in the Virgo cluster. Assuming that those are real motions, then some of those galaxies should have passed through the cluster core enough times to have some effect.
    No, the dynamical time scales are DEFINITELY too large. 1000 km/sec over megaparsecs is moving pretty slowly.

  22. #22
    Quote Originally Posted by dgruss23
    Thomas wrote: This is not how science works. If you submit an article to a peer reviewed journal and the referee detects an error or omission in the theory on which your data analysis is based, then you have to redo the data analysis with the modified theory, but you can't say: 'but there is other evidence that my conclusions are correct'.
    Not necessarily modify the theory. I've received referee reports in which the referee finds the analysis sound but wants to see more support for the conclusions.
    Sure, but then they did not question your underlying theory.

    Quote Originally Posted by dgruss23
    It is really hit or miss on referee's - and the scientific editors that oversee the refereeing of the paper - if you're trying to publish controversial views. From my experience, some referee's are tolerant of alternate views as long as the analysis is sound. Other referee's demand that the evidence for a controversial view be extremely compelling - even if they acknowledge the basic analysis looks sound.
    They are tolerant as long as your work is insignificant and does not challenge their own work.

    Quote Originally Posted by dgruss23
    Did I miss the references on your site? If you have not added them you should because it would go a long way toward demonstrating that you are taking a scientific approach.
    Most of the points addressed on my site are fundamental text-book topics which are self-explanatory and need no specific references. Others are based on my own work which I have referenced in numerous cases.
    If you take the topic addressed by me in this post for instance, this is solely my own idea and I could not possibly quote anybody else here, and for those interested in other theories of galactic rotation curves, I have indeed given a link where they can find hundreds of references if they want.
    Most of the proponents of the theories I criticize may probably not appreciate anyway if I quote them.

    By the way, I had work published in a peer reviewed journal, but the response was zero despite the original and controversial nature of the paper.
    In contrast, I get at least some sort of response from posting my work on the web.

  23. #23
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    Quote Originally Posted by Thomas
    By the way, I had work published in a peer reviewed journal, but the response was zero despite the original and controversial nature of the paper.
    In contrast, I get at least some sort of response from posting my work on the web.
    Can you give us a citation?

  24. #24
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    Thomas wrote: By the way, I had work published in a peer reviewed journal, but the response was zero despite the original and controversial nature of the paper.
    In contrast, I get at least some sort of response from posting my work on the web.
    That's Great (the first part about getting your work published)! I'm not surprised you didn't get a response from the scientific community, but do get more responses from the web. People have to be curious about discrepant results before you'll get any feedback. One difficulty is that there might be a discrepant result or alternate theory that addresses one phenomenon, but someone holding the mainstream view will look at that and say - "Well what about this and what about that."

    For example, JS has noted a number of different lines of evidence that he (and most researchers) feels supports the dark matter theory. In order to get any general response from the mainstream regarding your idea, you'll probably have to show that it is applicable to several more phenomenon.

    I think that is one reason why MOND (while not accepted by most) gets responses - including published critiques. Dark Matter proponents look at MOND and recognize that the MOND proponents are trying to explain spiral rotation curves - for high and low surface brightness galaxies and galaxy cluster dynamics among other things. So dark matter supporters have evaluated MOND for themselves.

    Thomas wrote: They are tolerant as long as your work is insignificant and does not challenge their own work.
    I think it depends a lot on the referee and the scientific editor. I’ve had two papers published (one with a co-author) and I’ve had one paper rejected. Ironically, the paper I had rejected was a much better paper than the one that was published – larger sample, better presentation, better data sources. The refereeing of the rejected paper is almost a comical story. The first referee report said that the paper SHOULD BE PUBLISHED, but that the conclusions were too speculative and it recommended a more critical look. So I took a more critical look, found the same result and presented the results with better figures. The second report again affirmed the paper was well written, but wanted me to use a different dataset. So I re-did the analysis again and once again found the same result. But this time the first referee was unavailable so it went to a new referee. After having the paper for about 5 weeks the new referee decided to “formally excuse” him/herself from refereeing the paper saying that it was too controversial and that he/she was “certainly not the person to sort it all out.” Note that if the referee had found serious flaws in the paper he/she could have simply rejected it at this point. However, this referee went on to add that the paper ought to be submitted to a different journal (even named it) that is more appropriate for alternate views. So I took a look at the paper and decided to shrink it down to the core result that I felt was most important to try to communicate. This time it goes to yet another referee and this person decides to reject specifically stating that it was not because of mistakes, but instead because the referee felt the paper misses the point. So I went from a recommendation that the paper be published to a recommendation that the paper be rejected – all the while repeatedly demonstrating with different data sets that the results come out the same. Does the paper miss the point? I think the referee missed a few points and I wrote a 5 page rebuttal to the scientific editor supporting my case. There was one particular point that the last referee made which I felt offered a way to improve the paper, so a few weeks ago I submitted another paper to a different journal. We’ll see what happens this time.

    I suppose this story probably supports your point more than contradicts it, but I really feel that had I had the same scientific editor as I had for the first paper that was accepted, I probably would have managed to get the second paper accepted. I’m not saying the second scientific editor was not patient and fair with me, but he had a different approach than the scientific editor of the first paper. In fact one major motivation for the second paper was a comment made by the referee of the first paper who said something to the effect of “Well, I still think the result is because of sample selection.” So I figured if I could demonstrate the result again with a much larger sample that could only be a good thing –and that what the second paper was about.

  25. #25
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    Quote Originally Posted by Tim Thompson
    Quote Originally Posted by Thomas
    Only charged particles with a velocity v=vD will therefore not experience any Lorentz force, i.e. this is the speed with which the plasma will be dragged along by the magnetic field.
    Backward physics. Its the plasma that does the dragging, not the field. Besides, the only way to exert a force on a charge with a magnetic field is through Faraday induction, which depends on dB/dt, and I don't see that in your first post anywhere. So even if the neutral gas becomes ionized, there's no way the magnetic field can add energy to the plasma unless there's a dB/dt between the plasma & the field.
    Wrong,if only you have read it the first time I post it it you will see how it really works.
    http://public.lanl.gov/alp/plasma/Pe...uurDec2000.pdf

    The concept of a critical ionization velocity (CIV )...
    If a neutral gas and a magnetized plasma are in relative motion.a rapid ionization of the neutrals take place if the kinetic energy of the neutral relative to the plasma exceeds the ionization potential cV2 of the neutrals..

  26. #26

    Re: Galactic Rotation and Dark Matter

    Quote Originally Posted by Thomas
    Also, a significant fraction of the photoelectrons (about 50% for electrons with an energy of 1 Rydberg (13.6 eV); see my website http://www.plasmafacts.de/recrsect.htm) will recombine into the ground state again, therewith restoring the UV photon.
    Quote Originally Posted by JS Princeton
    This is absolutely wrong. The electrons recombine to higher energy levels before reaching ground state. It is thermodynamically favorable for them NOT to recombine to the ground state because the energy difference represents a good estimation of cross-section. Rather, electron capture almost uniformly occurs to higher states
    No, I am afraid your information is incorrect. Recombination has nothing to do with Thermodynamics. It is an individual particle process and depends basically on the overlap integral of the wave functions for the free and bound state of the electron. I have worked on this problem extensively some years ago and you can find the results in the link I gave above.

    Quote Originally Posted by Thomas
    There is the further theoretical possibility of auto-ionization in the course of collisions of neutral atoms, which I have suggested to explain the nightime density of the earth's ionosphere (see my website http://www.plasmaphysics.org.uk/#auto). This would be completely independent of any radiation flux.
    Quote Originally Posted by JS Princeton
    Collisional ionization is nearly impossible. The temperatures required are absolutely enormous.
    Again, you did apparently not check out the link- reference: the energy could be provided by the atomic electrons by means of a purely classical coulomb collision.

  27. #27
    Quote Originally Posted by JS Princeton
    Quote Originally Posted by Thomas
    By the way, I had work published in a peer reviewed journal, but the response was zero despite the original and controversial nature of the paper.
    In contrast, I get at least some sort of response from posting my work on the web.
    Can you give us a citation?
    Check out my website http://www.plasmafacts.de . This sums up most of my works in quite some detail and you can also download the full manuscripts for the major ones (it does not really matter which ones are actually published in print, they are all equally well researched and (in my opinion) uninvalidated by the referees (you can be assured that I would have corrected obvious errors immediately)).

  28. #28
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    Quote Originally Posted by Thomas
    Check out my website http://www.plasmafacts.de . This sums up most of my works in quite some detail and you can also download the full manuscripts for the major ones (it does not really matter which ones are actually published in print
    Sure it matters, especially since you've made the claim. I see three published papers listed on your cv.

  29. #29
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    Re: Galactic Rotation and Dark Matter

    Quote Originally Posted by Thomas
    No, I am afraid your information is incorrect. Recombination has nothing to do with Thermodynamics. It is an individual particle process and depends basically on the overlap integral of the wave functions for the free and bound state of the electron. I have worked on this problem extensively some years ago and you can find the results in the link I gave above.
    Sorry, Thomas, your results are not done rigorously. Read Shu's library (volume 2, I believe) for the actual derivation. The details of your analysis are simply wrong because the fact remains that recombination of electrons occur to higher energy levels preferentially. That's just the way the cross sections work.

    Quote Originally Posted by Thomas
    There is the further theoretical possibility of auto-ionization in the course of collisions of neutral atoms, which I have suggested to explain the nightime density of the earth's ionosphere (see my website http://www.plasmaphysics.org.uk/#auto). This would be completely independent of any radiation flux.
    Again, you provide no citations to any experimental work that is done on "auto-ionization" which, as far as I know, is not a conceivable mechanism. Citing yourself is poor form, as far as I'm concerned, because you have demonstrated no reason for us to believe you.

    Quote Originally Posted by JS Princeton
    Again, you did apparently not check out the link- reference: the energy could be provided by the atomic electrons by means of a purely classical coulomb collision.
    Make the argument, this just doesn't make any sense. Atoms have to be warm to get beyond columb repulsion. Getting them to the point of ionization so that the repulsion of an exterior electron is greater than the attraction to the nucleus is a near impossibility. It's simply not going to happen.

  30. #30
    Quote Originally Posted by dgruss23
    I think that is one reason why MOND (while not accepted by most) gets responses - including published critiques. Dark Matter proponents look at MOND and recognize that the MOND proponents are trying to explain spiral rotation curves - for high and low surface brightness galaxies and galaxy cluster dynamics among other things. So dark matter supporters have evaluated MOND for themselves.
    In my opinion, MOND gets reponses (even from Dark Matter proponents) because it is indeed a rather far-fetched and unfounded theory: the inverse square law behaviour of gravitation (or the coulomb force) is not a consequence of physics but of the geometry of space; it merely reflects the fact that the 'flux' of gravity through a sphere around the mass is constant, and that a surface has 2 and not 1.9 or 2.1 dimensions. You cannot just change the laws of geometry in order to interprete physical data. Because of this conceptional flaw, I would say that the only thing that MOND achieves is taking the attention off more valid alternatives. So in this sense, it even indirectly supports the Dark Matter theory and people are happy to discuss it.

    Thomas wrote: They are tolerant as long as your work is insignificant and does not challenge their own work.
    Quote Originally Posted by dgruss23
    I think it depends a lot on the referee and the scientific editor. I’ve had two papers published (one with a co-author) and I’ve had one paper rejected. Ironically, the paper I had rejected was a much better paper than the one that was published – larger sample, better presentation, better data sources. The refereeing of the rejected paper is almost a comical story.......
    Your experience with referees and editors sounds rather familiar to me. With most of my unsuccessful attempts (about half a dozen), I went through all appeal stages available. In one case, I also had to start the review process all over again because the editor changed (just when I felt I was in good position in my argument with the referee); in another case, the editor just stopped replying to my appeal letters. The referees were less than helpful in most cases, usually using the same arguments against my paper that I was trying to invalidate in the first place (which makes any discussion really pointless). In some cases they were outright abusive (I should do my homework first etc.), at the same time hiding behind their anonymity (a not too uncommon phenomenon in discussion forums either I would like to add).
    The main reason why I have not sent any new work to journals anymore for the last 10 years is however my unemployment (lack of proper computing resources mainly), but with the increased possibilities of the internet, I would probably opt for self-publication now anyway. I feel that I can critically review my work myself, so that there should not be any crucial errors in it, and it costs less time and nerves. The downpoint is that at the moment non-peer-reviewed work is still classed as second-rate, but I hope this will soon change as well.

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